The invention relates to tissue and organ transplantation.
The invention provides methods of inducing tolerance to foreign antigens. The methods feature preparative regimens which minimize or eliminate the need for hematopoietic space-creating irradiation, especially, preparative whole body irradiation. In particular, it has been discovered that the administration of a relatively large number of stem cells, combined with the creation of thymic space, can allow the induction of tolerance without the need for whole body irradiation (WBI).
Accordingly, the invention features a method of inducing tolerance in a recipient mammal of a first species to a graft from a donor mammal of a second species. The method includes: introducing, e.g., by intravenous injection, into the recipient mammal, hematopoietic stem cells; and preferably, implanting the graft in the recipient. The hematopoietic cells are believed to prepare the recipient for the graft that follows, by inducing tolerance at both the B-cell and T-cell levels.
The recipient mammal can be, by way of example, a human. The donor mammal can be, by way of example, a swine, e.g., a miniature swine. The graft is preferably from a discordant species. The graft preferably expresses a major histocompatibility complex (MHC) antigen, preferably a class II antigen. In particularly preferred embodiments the recipient is a primate, e.g., a human, and the donor is a swine, e.g., a miniature swine.
As is discussed elsewhere herein, the inventors have discovered that this method can be practiced without the administration of hematopoietic space-creating irradiation, e.g., whole body irradiation. Whole body irradiation is often used in the art to create hematopoietic space and thus promote engraftment, chimerism, and tolerance. The need for hematopoietic space-creating irradiation can be reduced or entirely eliminated by the inclusion of one or more of the following steps in the method:
(1) Administering a sufficiently large number of donor hematopoietic cells to the recipient such that, donor stem cells engraft, give rise to mixed chimerism, and induce tolerance, preferably the stem cells are administered either in combination with one or more of the treatments disclosed herein, e.g., (2), (3), or (4) described immediately below;
(2) Administering hematopoietic space creating antibodies or drugs to the recipient. E.g., administering an inhibitor of cell proliferation, e.g., DSG, or an anti-metabolite, e.g. brequinar, or an anti-T cell antibody, e.g., one or both of an anti-CD4 or anti-CD8 antibody.
(3) providing treatments (other than whole body irradiation) which promote engraftment and the formation of mixed chimerism by enhancing the ability of donor cells to compete with host bone marrow cells, e.g., administering stromal cells or administering donor specific growth factors or cytokines, e.g., where the donor is a miniature swine, administering one or more of swine SCF, swine IL-3, or swine GM-SCF, to the recipient.
(4) creating thymic space in the recipient, e.g., by irradiating the thymus of the recipient, e.g., by administering between 100 and 1,000, more preferably between 300 and 700, e.g., 700 rads, of thymic irradiation, or by administering anti-T cell antibodies in sufficient dose to inactivate thymocytes. Other methods for the creation of thymic space include: the administration of steroids, corticosteroids, brequinar, or an immune suppressant chemical or drug, e.g., rapamycin, cyclosporin, or FK506. Treatment to create thymic space should be administered, or at least begun, prior to the administration of hematopoietic stem cells. An effective treatment should deplete single positive thymocytes to an extent that engraftment and the formation of mixed chimerism is optimized in the absence of the creation of hematopoietic space, e.g., hematopoietic space created by whole body irradiation. In preferred embodiments the subject""s single positive thymocytes are depleted by at least 20, 40, 60, or 80%. Treatments which result in between 10 and 90% depletion are preferred. The length of the treatment will vary with dosage and the effectiveness of the agent but will generally be less than 60, 30, or 15 days. The treatment should last at least 7, and more preferably 10, or 14 days in length. In preferred courses of treatment, e.g., the administration of an immunosupressive chemical or drug, e.g., cyclosporine, should last between 7 and 30 days. The treatment, e.g., the administration of cyclosporin, should be started at a time such that it is completed prior to the administration of stem cells. Administration of the agent should be on a daily basis or as needed to maintain a level of the agent which allows the desired level of depletion. A particularly preferred treatment is the administration of an immunosuppresive chemical, e.g., cyclosporin, for more than 7 and less than 30 days. A useful regimen in rodents is 20 mg/kg/day cyclosporin for 14 days ending on the third day before administration of stem cells.
Thus, in preferred embodiments a quantity of hematopoietic stem cells sufficient to induce tolerance, without the need for hematopoietic space-creating irradiation, is administered to the recipient. In preferred embodiments the number of donor hematopoietic cells is at least twice, is at least equal to, or is at least 75, 50, or 25% as great as, the number of bone marrow cells found in an adult of the recipient species. In preferred embodiments the number of donor hematopoietic stem cells is at least twice, is at least equal to, or is at least 75, 50, or 25% as great as, the number of bone marrow hematopoietic stem cells found in an adult of the recipient species. In the case where an inbred population of the donor species exists, e.g., where the donor species is miniature swine, the number of available donor cells is not limited to the number of cells which can be obtained from a single animal. Thus, in such cases, the donor cells administered to the recipient can come from more than one, e.g., from two, three, four, or more animals. As is discussed below the donor stem cells can be provided in two or more separate administrations.
In preferred embodiments, mixed chimerism is induced in the recipient and the state of mixed chimerism is formed in the absence of the induction of hematopoietic space, e.g., in the absence of hematopoietic space created by space creating irradiation, e.g., whole body irradiation.
The number of donor cells administered to the recipient can be increased by either increasing the number of stem cells provided in a particular administration or by providing repeated administrations of donor stem cells.
Repeated stem cell administration can promote engraftment, mixed chimerism, and long-term deletional tolerance in graft recipients. Thus, the invention also includes methods in which multiple hematopoietic stem cell administrations are provided to a recipient. Multiple administration can substantially reduce or eliminate the need for hematopoietic space-creating irradiation. Administrations can be given prior to, at the time of, or after graft implantation. In preferred embodiments multiple administrations of stem cells are provided prior to the implantation of a graft. Two, three, four, five, or more administrations can be provided. The period between administrations of hematopoietic stem cells can be varied. In preferred embodiments a subsequent administration of hematopoietic stem cell is provided: at least two days, one week, one month, or six months after the previous administration of stem cells; when the recipient begins to show signs of host lymphocyte response to donor antigen; when the level of chimerism decreases; when the level of chimerism falls below a predetermined value; when the level of chimerism reaches or falls below a level where staining with a monoclonal antibody specific for a donor PBMC antigen is equal to or falls below staining with an isotype control which does not bind to PBMC""s, e.g. when the donor specific monoclonal stains less than 1-2% of the cells; or generally, as is needed to maintain a level of mixed chimerism sufficient to maintain tolerance to donor antigen.
One or more post graft-implantation-administrations of donor stem cells can also be provided to minimize or eliminate the need for irradiation. Post graft administration of hematopoietic stem cell can provided: at least two days, one week, one month, or six months after the previous administration of stem cells; at least two days, one week, one month, six months, or at any time in the life span of the recipient after the implantation of the graft; when the recipient begins to show signs of rejection, e.g., as evidenced by a decline in function of the grafted organ, by a change in the host donor specific antibody response, or by a change in the host lymphocyte response to donor antigen; when the level of chimerism decreases; when the level of chimerism falls below a predetermined value; when the level of chimerism reaches or falls below a level where staining with a monoclonal antibody specific for a donor PBMC antigen is equal to or falls below staining with an isotype control which does not bind to PBMC""s, e.g. when the donor specific monoclonal stains less than 1-2% of the cells; or generally, as is needed to maintain tolerance or otherwise prolong the acceptance of a graft.
When multiple stem cell administrations are given one or more of the administrations can include a number of donor hematopoietic cells which is at least twice, is equal to, or is at least 75, 50, or 25% as great as, the number of bone marrow cells found in an adult of the recipient species; include a number of donor hematopoietic stem cells which is at least twice, is equal to, or is at least 75, 50, or 25% as great as, the number of bone marrow hematopoietic stem cells found in an adult of the recipient species.
In preferred embodiments the method includes inactivating natural killer cells, preferably graft reactive or xenoreactive, e.g., swine reactive, NK cells, of the recipient mammal. This can be accomplished, e.g., by introducing into the recipient mammal an antibody capable of binding to natural killer cells of the recipient mammal. The administration of antibodies, or other treatment to inactivate natural killer cells, can be given prior to introducing the hematopoietic stem cells into the recipient mammal or prior to implanting the graft in the recipient. This antibody can be the same or different from an antibody used to inactivate T cells.
In preferred embodiments the method includes inactivating T cells, preferably graft reactive or xenoreactive, e.g., swine reactive, T cells of the recipient mammal. This can be accomplished, eg., by introducing into the recipient mammal an antibody capable of binding to T cells of the recipient mammal. The administration of antibodies, or other treatment to inactivate T cells, can be given prior to introducing the hematopoietic stem cells into the recipient mammal or prior to implanting the graft in the recipient. This antibody can be the same or different from an antibody used to inactivate natural killer cells.
One source of anti-NK antibody is anti-human thymocyte polyclonal anti-serum. Preferably, a second anti-mature T cell antibody can be administered as well, which lyses T cells as well as NK cells. Lysing T cells is advantageous for both bone marrow and graft survival. Anti-T cell antibodies are present, along with anti-NK antibodies, in anti-thymocyte anti-serum. Repeated doses of antibodies, e.g., anti-NK or anti-T cell antibodies, may be preferable. Monoclonal preparations can be used in the methods of the invention.
In preferred embodiments the recipient does not receive treatments which stimulate the release of a cytokine by mature T cells. E.g., the recipient should not receive a substance, e.g., a steroid drug, e.g., Prednisone (17, 21-dihydroxypregna-1, 4-diene-3, 11, 20-trione), at a dosage or concentration which stimulates the release of a cytokine by mature T cells in the recipient. Preferably, the recipient is free of such treatment from the time stem cells are first administered until the graft is implanted or until mixed chimerism and tolerance is established.
In preferred embodiments the method includes the administration of a short course of help reducing treatment, e.g., a drug or other chemical agent, which induces tolerance to unmatched class I and/or minor antigens on the graft which is introduced into the recipient. The short course of help reducing treatment, e.g., a short course of high dose cyclosporine, is generally administered at the time at the graft is introduced into the recipient. The duration of the short course of help reducing treatment is approximately equal to or is less than the period required for mature T cells of the recipient species to initiate rejection of an antigen after first being stimulated by the antigen; in more preferred embodiments, the duration is approximately equal to or is less than two, three, four, five, or ten times, the period required for a mature T cell of the recipient species to initiate rejection of an antigen after first being stimulated by the antigen. These methods are described in more detail in co-owned application Ser. No. 08/458,720, filed Jun. 1, 1995, which is hereby incorporated by references. Methods of Ser. No. 08/458,720 can be combined with the methods described herein.
Other preferred embodiments include: the step of introducing into the recipient mammal, donor species-specific stromal tissue, preferably hematopoietic stromal tissue, e.g., fetal liver or thymus. In preferred embodiments: the stromal tissue is introduced simultaneously with, or prior to, the hematopoietic stem cells; the hematopoietic stem cells are introduced simultaneously with, or prior to, the antibody.
Other preferred embodiments include treatments to further inactivate recipient T cells, particularly thymic or lymph node thymocytes or T cells. Thymic or lymph node thymocytes or T cells might otherwise inhibit the engraftment or survival of the administered cells. Such inactivation can be accomplished by one or more of; irradiating the thymus of the recipient mammal with a dose of radiation sufficient to inactivate thymocytes, e.g., 100-1,000, more preferably between 300 and 700, e.g., about 350 or 700 rads of thymic irradiation; administering one or repeated doses of an anti-T cell or anti-thymocyte antibody; or administering to the recipient a short course of an immunosuppressant chemical or drug, as is described herein. Inactivation of thymocytes or T cells can be performed prior to hematopoietic stem cell or graft transplantation. In preferred embodiments the method includes diminishing or inhibiting thymocyte or T cell activity, preferably the activity of thymic or lymph node T cells by administering to the recipient a short course of an immunosuppressive agent, e.g., a chemical or drug, e.g., cyclosporine, sufficient to inactivate thymocytes or T cells, preferably thymic or lymph node T cells. The duration of the short course of immunosuppressive agent is:
approximately equal to 30 days; approximately equal to or less than 8-12 days, preferably about 10 days; approximately equal to or less than two, three, four, five, or ten times the 8-12 or 10 day period. The short course can begin: before or at about the time the treatment to induce tolerance is begun, e.g., at about the time stem cells are introduced into the recipient; on the day the treatment to induce tolerance is begun, e.g., on the day stem cells are introduced into the recipient; within 1, 2, 4, 6, 8, 10, or 30 days before or after the treatment to induce tolerance is begun, e.g., within 1, 2, 4, 6, 8, 10, or 30 days before or after stem cells are introduced into the recipient. The short course of an immunosuppressive can be administered in conjunction with an anti-T cell antibody The short course of an immunosuppressive should be sufficient in concentration and duration to inactivate T cells, e.g., thymic or lymph node T cells, which would not be inactivated by antibody-based inactivation of T cells, e.g., inactivation by intravenous administrations of ATG antibody, or similar, preparations.
Other embodiments include (optionally): the step of, prior to hematopoietic stem cell transplantation, creating hematopoietic space, e.g., by irradiating the recipient mammal with low dose, e.g., less than 400, preferably less than 300, more preferably less than 200 or 100 rads, whole body irradiation to deplete or partially deplete the bone marrow of the recipient. As is discussed herein this treatment can be reduced or entirely eliminated.
Other preferred embodiments include: the step of, preferably prior to hematopoietic stem cell transplantation, depleting natural antibodies from the blood of the recipient mammal. Depletion can be achieved, by way of example, by contacting the recipients blood with an epitope which absorbs preformed anti-donor antibody. The epitope can be coupled to an insoluble substrate and provided, e.g., as an affinity column. E.g., an xcex11-3 galactose linkage epitope-affinity matrix, e.g., matrix bound linear B type VI carbohydrate, can be used to deplete natural antibodies. Depletion can also be achieved by hemoperfusing an organ, e.g., a liver or a kidney, obtained from a mammal of the donor species. (In organ hemoperfasion antibodies in the blood bind to antigens on the cell surfaces of the organ and are thus removed from the blood.)
Other preferred embodiments include those in which: the same mammal of the second species is the donor of one or both the graft and the hematopoietic cells; and the antibody is an anti-human thymocyte polyclonal anti-serum, obtained, e.g., from a horse or pig.
In preferred embodiments, the method includes the step of introducing into the recipient a graft obtained from the donor which is obtained from a different organ than the hematopoietic stem cells, e.g., a heart, pancreas, liver, or kidney.
Methods of the invention which substantially reduce or eliminate the need for hematopoietic space creating irradiation can be used when implanting allogeneic stem cells. Accordingly, in another aspect, the invention features a method of inducing tolerance in a recipient mammal of a first species to a graft from a donor mammal of the same species. The recipient mammal can be, by way of example, a primate, e.g., a human. The graft preferably expresses a major histocompatibility complex (MHC) antigen, preferably a class II antigen.
The method includes: introducing, e.g., by intravenous injection, into the recipient mammal, hematopoietic stem cells; and preferably, implanting the graft in the recipient. The hematopoietic cells are believed to prepare the recipient for the graft that follows, by inducing tolerance at both the B-cell and T-cell levels.
This method can be practiced without the administration of hematopoietic space-creating irradiation, e.g., whole body irradiation. Whole body irradiation is often used in the art to create hematopoietic space and thus promote engraftment, chimerism, and tolerance. The need for hematopoietic space-creating irradiation can be reduced or entirely eliminated by inclusion of one or more of the following steps in the method:
(1) Administering a sufficiently large number of donor hematopoietic cells to the recipient such that donor stem cells engraft, give rise to mixed chimerism, and induce tolerance, preferably, the stem cells are administered in combination with one or more of the treatments disclosed herein, e.g., (2) or (3) immediately below,;
(2) Administering hematopoietic space creating antibodies or drugs to the recipient. E.g., administering an inhibitor of cell proliferation, e.g., DSG, or an anti-metabolite, e.g. brequinar, or an anti-T cell antibody, e.g., one or both of an anti-CD4 or anti-CD8 antibody.
(3) creating thymic space in the recipient, e.g., by irradiating the thymus of the recipient, e.g., by administering between 100 and 1,000, more preferably between 300 and 700, e.g., 700 rads, of thymic irradiation, or by administering anti-T cell antibodies in sufficient dose to inactivate thymocytes. Other methods for the creation of thymic space include: the administration of steroids, corticosteroids, brequinar or an immune suppressant chemical or drug, e.g, rapamycin, cyclosporin, or FK506. Treatment to create thymic space should be administered, or at least begun, prior to the administration of hematopoietic stem cells. An effective treatment should deplete single positive thymocytes to an extent that engraftment and the formation of mixed chimerism is optimized in the absence of the creation of hematopoietic space, e.g., hematopoietic space created by whole body irradiation. In preferred embodiments the subject""s single positive thymocytes are depleted by at least 20, 40, 60, or 80%. Treatments which result in between 10 and 90% depletion are preferred. The length of the treatment will vary with dosage and the effectiveness of the agent but will generally be less than 60, 30, or 15 days. The treatment should last at least 7, and more preferably 10, or 14 days in length. In preferred courses of treatment, e.g., the administration of an immunosupressive chemical or drug, e.g., cyclosporine, should last between 7 and 30 days. The treatment, e.g., the administration of cyclosporin, should be started at a time such that it is completed prior to the administration of stem cells. Administration of the agent should be on a daily basis or as needed to maintain a level of the agent which allows the desired level of depletion. A particularly preferred treatment is the administration of an immunosuppresive chemical, e.g., cyclosporin, for more than 7 and less than 30 days. A useful regimen in rodents is 20 mg/kg/day cyclosporin for 14 days ending on the third day before administration of stem cells.
Thus, in preferred embodiments a quantity of hematopoietic stem cells sufficient to induce tolerance, without the need for hematopoietic space-creating irradiation, is administered to the recipient. In preferred embodiments the number of donor hematopoietic cells is at least twice, is at least equal to, or is at least 75, 50, or 25% as great as, the number of bone marrow cells found in an adult of the recipient species. In preferred embodiments the number of donor hematopoietic stem cells is at least twice, is at least equal to, or is at least 75, 50, or 25% as great as, the number of bone marrow hematopoietic stem cells found in an adult of the recipient species.
In preferred embodiments, mixed chimerism is induced in the recipient and the state of mixed chimerism is formed in the absence of the induction of hematopoietic space, e.g., in the absence of hematopoietic space created by space creating irradiation, e.g., whole body irradiation.
The number of donor cells administered to the recipient can be increased by either or both of increasing the number of stem cells provided in a particular administration or by providing repeated administrations of donor stem cells.
Repeated stem cell administration can promote engraftment, mixed chimerism, and long-term deletional tolerance in graft recipients. Thus, the invention also includes methods in which multiple hematopoietic stem cells administrations are provided to a recipient. Multiple administration can substantially reduce or eliminate the need for hematopoietic space-creating irradiation. Administrations can be given prior to, at the time of, or after graft implantation. In preferred embodiments multiple administrations of stem cells are provided prior to the implantation of a graft. Two, three, four, five, or more administrations can be provided. The period between administrations of hematopoietic stem cells can be varied. In preferred embodiments a subsequent administration of hematopoietic stem cell is provided: at least two days, one week, one month, or six months after the previous administration of stem cells; when the recipient begins to show signs of host lymphocyte response to donor antigen; when the level of chimerism decreases; when the level of chimerism falls below a predetermined value; when the level of chimerism reaches or falls below a level where staining with a monoclonal antibody specific for a donor PBMC antigen is equal to or falls below staining with an isotype control which does not bind to PBMC""s, e.g. when the donor specific monoclonal stains less than 1-2% of the cells, or generally, as is needed to maintain a level of mixed chimerism sufficient to maintain tolerance to donor antigen.
One or more post graft-implantation-administrations of donor stem cells can also be provided to minimize or eliminate the need for irradation. Post graft administration of hematopoietic stem cell can provided: at least two days, one week, one month, or six months after the previous administration of stem cells; at least two days, one week, one month, six months, or at any time in the life span of the recipient after the implantation of the graft; when the recipient begins to show signs of rejection, e.g., as evidenced by a decline in function of the grafted organ, by a change in the host donor specific antibody response, or by a change in the host lymphocyte response to donor antigen; when the level of chimerism decreases; when the level of chimerism falls below a predetermined value; when the level of chimerism reaches or falls below a level where staining with a monoclonal antibody specific for a donor PBMC antigen is equal to or falls below staining with an isotype control which does not blind to PBMC""s, e.g. when the donor specific monoclonal stains less than 1-2% of the cells; or generally, as is needed to maintain tolerance or otherwise prolong the acceptance of a graft.
When multiple stem cell administrations are given one or more of the administrations can: include a number of donor hematopoietic cells which is at least twice, is equal to, or is at least 75, 50, or 25% as great as, the number of bone marrow cells found in an adult of the recipient species; include a number of donor hematopoietic stem cells which is at least twice, is equal to, or is at least 75, 50, or 25% as great as, the number of bone marrow hematopoietic stem cells found in an adult of the recipient species.
In preferred embodiments the method includes inactivating natural killer cells, preferably graft reactive or donor reactive NK cells, of the recipient mammal. This can be accomplished, e.g., by introducing into the recipient mammal an antibody capable of binding to natural killer cells of the recipient mammal. The administration of antibodies, or other treatment to inactivate natural killer cells, can be given prior to introducing the hematopoietic stem cells into the recipient mammal or prior to implanting the graft in the recipient. This antibody can be the same or different from an antibody used to inactivate T cells.
In preferred embodiments the method includes inactivating T cells, preferably graft reactive or donor reactive T cells, of the recipient mammal. This can be accomplished, e.g., by introducing into the recipient mammal an antibody capable of binding to T cells of the recipient mammal. The administration of antibodies, or other treatment to inactivate T cells, can be given prior to introducing the hematopoietic stem cells into the recipient mammal or prior to implanting the graft in the recipient. This antibody can be the same or different from an antibody used to inactivate natural killer cells.
One source of anti-NK antibody is anti-human thymocyte polyclonal anti-serum. Preferably, a second anti-mature T cell antibody can be administered as well, which lyses T cells as well as NK cells. Lysing T cells is advantageous for both bone marrow and graft survival. Anti-T cell antibodies are present, along with anti-NK antibodies, in anti-thymocyte anti-serum. Repeated doses of antibodies, e.g., anti-NK or anti-T cell antibodies, may be preferable. Monoclonal preparations can be used in the methods of the invention.
In preferred embodiments the recipient does not receive treatments which stimulate the release of a cytokine by mature T cells. E.g., the recipient should not receive a substance, e.g., a steroid drug, e.g., Prednisone (17, 21-dihydroxypregna-1, 4-diene-3, 11, 20-trione), at a dosage or concentration which stimulates the release of a cytokine by mature T cells in the recipient. Preferably, the recipient is free of such treatment from the time stem cells are first administered until the graft is implanted or until mixed chimerism and tolerance is established.
In preferred embodiments the method includes the administration of a short course of help reducing treatment, e.g., a drug or other chemical, which induces tolerance to unmatched class I and/or minor antigens on the graft which is introduced into the recipient. The short course of help reducing treatment, e.g., a short course of high dose cyclosporine, is generally administered at the time at the graft is introduced into the recipient. The duration of the short course of help reducing treatment is approximately equal to or is less than the period required for mature T cells of the recipient species to initiate rejection of an antigen after first being stimulated by the antigen; in more preferred embodiments, the duration is approximately equal to or is less than two, three, four, five, or ten times, the period required for a mature T cell of the recipient species to initiate rejection of an antigen after first being stimulated by the antigen. These methods are described in more detail in co-owned application Ser. No. 08/458,720, filed Jun. 1, 1995, which is hereby incorporated by references. Methods of Ser. No. 08/458,720 can be combined with the methods described herein.
Other preferred embodiments include treatments to further inactivate recipient T cells, particularly thymic or lymph node thymocytes or T cells. Thymic or lymph node thymocytes or T cells might otherwise inhibit the engraftment or survival of the administered cells. Such inactivation can be accomplished by one or more of: irradiating the thymus of the recipient mammal with a dose of radiation sufficient to inactivate thymocytes, e.g., 100-1,000, more preferably between 300 and 700, e.g., about 350 or 700 rads of thymic irradiation; administering one or repeated doses of an anti-T cell or anti-thymocyte antibody; or administering to the recipient a short course of an immunosuppressant chemical or drug, as is described herein. Inactivation of thymocytes or T cells can be performed prior to hematopoietic stem cell or graft transplantation. In preferred embodiments the method includes diminishing or inhibiting thymocyte or T cell activity, preferably the activity of thymic or lymph node T cells by administering to the recipient a short course of an immunosuppressive agent, e.g., cyclosporine, sufficient to inactivate thymocytes or T cells, preferably thymic or lymph node T cells. The duration of the short course of immunosuppressive agent is: approximately equal to 30 days; approximately equal to or less than 8-12 days, preferably about 10 days; approximately equal to or less than two, three, four, five, or ten times the 8-12 or 10 day period. The short course can begin: before or at about the time the treatment to induce tolerance is begun, e.g., at about the time stem cells are introduced into the recipient; on the day the treatment to induce tolerance is begun, e.g., on the day stem cells are introduced into the recipient; within 1, 2, 4, 6, 8, 10, or 30 days before or after the treatment to induce tolerance is begun, e.g., within 1, 2, 4, 6, 8, 10, or 30 days before or after stem cells are introduced into the recipient. The short course of an immunosuppressive can be administered in conjunction with an anti-T cell antibody. The short course of an immunosuppressive should be sufficient in concentration and duration to inactivate T cells, e.g., thymic or lymph node T cells, which would not be inactivated by antibody-based inactivation of T cells, e.g., inactivation by intravenous administrations of ATG antibody, or similar, preparations.
Other embodiments include (optionally): the step of, prior to hematopoietic stem cell transplantation, creating hematopoietic space, e.g., by irradiating the recipient mammal with low dose, e.g., less than 400, preferably less than 300, more preferably less than 200 or 100 rads, whole body irradiation to deplete or partially deplete the bone marrow of the recipient. As is discussed herein this treatment can be reduced or entirely eliminated.
In another aspect, the invention features a method of inducing tolerance to, or prolonging acceptance of, a graft from a donor mammal. The method includes: diminishing or inhibiting thymocyte or T cell activity, preferably the activity of thymic or lymph node T cells, by administering to the recipient, a short course of an immunosuppressive agent, e.g., a drug or other chemical, e.g., cyclosporine, sufficient to inactivate thymocytes or T cells, preferably thymic or lymph node T cells. The duration of the short course of immunosuppressive agent is: approximately equal to 30 days; approximately equal to or less than 8-12 days, preferably about 10 days; approximately equal to or less than two, three, four, five, or ten times the 8-12 or 10 day period. The short course can begin: before the introduction of door tissue into the recipient, preferably and will end 1, 2, 4, 6, 8, 10, or 30 days before introduction of donor tissue,
In preferred embodiments: the recipient is a primate, e.g., a human, and the graft is an allograft; the recipient is a primate, e.g., a human, and the donor is from a second species, e.g., a second primate species or a swine.
This method can be combined with any of the other methods described herein.
xe2x80x9cDiscordant species combinationxe2x80x9d, as used herein, refers to two species in which hyperacute rejection occurs when a graft is grafted from one to the other. Generally, discordant species are from different orders, while non-discordant species are from the same order. For example, rats and mice are non-discordant concordant species. Concordant species combinations do not exhibit hyperacute rejection.
xe2x80x9cGraftxe2x80x9d, as used herein, refers to a body part, organ, tissue, or cells. Organs such as liver, kidney, heart or lung, or other body parts, such as bone or skeletal matrix, tissue, such as skin, intestines, endocrine glands, or progenitor stem cells of various types, are all examples of grafts.
xe2x80x9cHelp reducing agentxe2x80x9d, as used herein, is an agent, e.g., an immunosuppressive drug, which results in the reduction of cytokine release. Examples of help reducing agents are cyclosporine, FK-506, and rapamycin. Anti-T cell antibodies, because they can eliminate T cells, are not preferred for use as help reducing agents. A help reducing agent must be administered in sufficient dose to give the level of inhibition of cytokine release which will result in tolerance. The help reducing agent should be administered in the absence of treatments which promote cytokine, e.g., IL-2, release. Putative help reducing agents can be prescreened by in vitro or in vivo tests, e.g., by contacting the putative agent with T cells and determining the ability of the treated T cells to release a cytokine, e.g., IL-2. The inhibition of cytokine release is indicative of the putative agent""s efficacy as a help reducing agent. Such prescreened putative agents can then be further tested in a kidney transplant assay. In a kidney transplant assay a putative help reducing agent is tested for efficacy by administering the putative agent to a recipient monkey and then implanting a kidney from a class II matched class I and minor antigen mismatched donor monkey into the recipient. Tolerance to the donor kidney (as indicated by prolonged acceptance of the graft) is indicative that the putative agent is, at the dosage tested, a help reducing agent.
xe2x80x9cHelp reductionxe2x80x9d, as used herein, means the reduction of T cell help by the inhibition of the release of at least one cytokine, e.g., any of IL-2, IL-4, IL-6, gamma interferon, or TNF, from T cells of the recipient at the time of the first exposure to an antigen to which tolerance is desired. The inhibition induced in a recipient""s T cell secretion of a cytokine must be sufficient such that the recipient is tolerized to an antigen which is administered during the reduction of help. Although not being bound by theory, it is believed that the level of reduction is one which substantially eliminates the initial burst of IL-2 which accompanies the first recognition of a foreign antigen but which does not eliminate all mature T cells, which cells may be important in educating and producing tolerance.
xe2x80x9cHematopoietic spacexe2x80x9d, as used herein, refers to a condition created in the bone marrow which promotes engraftment of administered stem cells. The most common way of creating hematopoietic space is by irradiation of the bone marrow with whole body irradiation.
xe2x80x9cHematopoietic stem cellxe2x80x9d, as used herein, refers to a cell, e.g., a bone marrow cell, or a fetal liver or spleen cell, which is capable of developing into all myeloid and lymphoid lineages and by virtue of being able to self-renew can provide long term hematopoietic reconstitution. Purified preparations of hematopoietic cells or preparations, such as bone marrow, which include other cell types, can be used in methods of the invention. Although not wishing to be bound by theory, it is believed that the hematopoietic stem cells home to a site in the recipient mammal. The preparation should include immature cells, i.e., undifferentiated hematopoietic stem cells; these desired cells can be separated out of a preparation or a complex preparation can be administered. E.g., in the case of bone marrow stem cells, the desired primitive cells can be separated out of a preparation or a complex bone marrow sample including such cells can be used. Hematopoietic stem cells can be from fetal, neonatal, immature or mature animals. Stem cells derived from the cord blood of the recipient or the donor can be used in methods of the invention. See U.S. Pat. No. 5,192,553, hereby incorporated by reference, and U.S. Pat. No. 5,004,681, hereby incorporated by reference.
xe2x80x9cImmunosuppressive agent capable of inactivating thymic or lymph node T cellsxe2x80x9d, as used herein, is an agent, e.g., a chemical agent, e.g., a drug, which, when administered at an appropriate dosage, results in the inactivation of thymic or lymph node T cells. Examples of such agents are cyclosporine, FK-506, and rapamycin. Anti-T cell antibodies can also be used. An agent should be administered in sufficient dose to result in significant inactivation of thymic or lymph node T cells which are not inactivated by administration of an anti-T cell antibody, e.g., an anti-ATG preparation. Putative agents, and useful concentrations thereof, can be prescreened by in vitro or in vivo tests, e.g., by administering the putative agent to a test animal, removing a sample of thymus or lymph node tissue, and testing for the presence of active T cells in an in vitro or in vivo assay. Such prescreened putative agents can then be further tested in transplant assays.
xe2x80x9cThymic or lymph node or thymocytes or T cellxe2x80x9d, as used herein, refers to thymocytes or T cells which are resistant to inactivation by traditional methods of T cell inactivation, e.g., inactivation by a single intravenous administration of anti-T cell antibodies, e.g., anti-bodies, e.g., ATG preparation.
xe2x80x9cThymic irradiationxe2x80x9d, as used herein, refers to a treatment in which at least half, and preferably at least 75, 90, or 95% of the administered irradiation is targeted to the thymus. Whole body irradiation, even if the thymus is irradiated in the process of delivering the whole body irradiation, is not considered thymic irradiation.
xe2x80x9cMHC antigenxe2x80x9d, as used herein, refers to a protein product of one or more MHC genes; the term includes fragments or analogs of products of MHC genes which can evoke an immune response in a recipient organism. Examples of MHC antigens include the products (and fragments or analogs thereof) of the human MHC gene, i.e., the HLA genes. MHC antigens in swine, e.g., miniature swine, include the products (and fragments and analogs thereof) of the SLA genes, e.g., the DRB gene.
xe2x80x9cMiniature swinexe2x80x9d, as used herein, refers to a wholly or partially inbred pig.
xe2x80x9cHematopoietic space-creating irradiationxe2x80x9d, as used herein, refers to irradiation directed to the hematopoietic tissue, i.e., to tissue in which stem cells are found, e.g., the bone marrow. It is of sufficient intensity to kill or inactivate a substantial number of hematopoietic cells. It is often given as whole body irradiation.
xe2x80x9cThymic spacexe2x80x9d as used herein, is a state created by a treatment that facilitates the migration to and/or development in the thymus of donor hematopoietic cells of a type which can delete or inactivate host thymocytes that recognize donor antigens. It is believed that the effect is mediated by elimination of host cells in the thymus.
xe2x80x9cShort course of a help reducing agentxe2x80x9d, as used herein, means a transitory non-chronic course of treatment. The treatment should begin before or at about the time of transplantation of the graft. Alternatively, the treatment can begin before or at about the time of the recipient""s first exposure to donor antigens. Optimally, the treatment lasts for a time which is approximately equal to or less than the period required for mature T cells of the recipient species to initiate rejection of an antigen after first being stimulated by the antigen. The duration of the treatment can be extended to a time approximately equal to or less than two, three, four, five, or ten times, the period required for a mature T cell of the recipient species to initiate rejection of an antigen after first being stimulated by the antigen. The duration will usually be at least equal to the time required for mature T cells of the recipient species to initiate rejection of an antigen after first being stimulated by the antigen. In pigs and monkeys, about 12 days of treatment is sufficient. Experimenting with cyclosporine A (10 mg/kg) in pigs show that 6 days is not sufficient. Other experiments in monkeys show that IL-2 administered on day 8, 9, or 10 of cyclosporine A treatment will result in rejection of the transplanted tissue. Thus, 8, 9, or 10 days is probably not sufficient in pigs. In monkeys, a dose of 10 mg/kg cyclosporine with a blood level of about 500-1,000 ng/ml is sufficient to induce tolerance to class II matched class I and minor antigen mismatched kidneys. The same blood level, 500-1,000 ng/ml, is sufficient to induce tolerance in pigs. Long-term administration of 5 mg/kg prevents rejection (by long term immune suppression) but does not result in tolerance.
xe2x80x9cShort course of a immunosuppressive agentxe2x80x9d, as used herein, means a transitory non-chronic course of treatment, The treatment should begin before or at about the time the treatment to induce tolerance is begun, e.g., at about the time, xenogeneic, allogeneic, genetically engineered syngeneic, or genetically engineered autologous stem cells are introduced into the recipient. e.g., the short course can begin on the day the treatment to induce tolerance is begun, e.g., on the day, xenogeneic, allogeneic, genetically engineered syngeneic, or genetically engineered autologous stem cells are introduced into the recipient or the short course can begin within 1, 2, 4, 6, 8, or 10 days before or after the treatment to induce tolerance is begun, e.g., within 1, 2, 4, 6, 8, or 10 days before or after xenogeneic, allogeneic, genetically engineered syngeneic, or genetically engineered autologous stem cells are introduced into the recipient. The short course can last for: a period equal to or less than about 8-12 days, preferably about 10 days, or a time which is approximately equal to or is less than two, three, four, five, or ten times the 8-12 or 10 day period. Optimally, the short course lasts about 30 days. The dosage should be sufficient to maintain a blood level sufficient to inactivate thymic or lymph node T cells. A dosage of approximately 15 mg/kg/day has been found to be effective in primates.
xe2x80x9cStromal tissuexe2x80x9d, as used herein, refers to the supporting tissue or matrix of an organ, as distinguished from its functional elements or parenchyma.
xe2x80x9cTolerancexe2x80x9d, as used herein, refers to an inhibition of a graft recipient""s immune response which would otherwise occur, e.g., in response to the introduction of a nonself MHC antigen into the recipient. Tolerance can involve humoral, cellular, or both humoral and cellular responses. Tolerance, as used herein, refers not only to complete immunologic tolerance to an antigen, but to partial immunologic tolerance, i.e., a degree of tolerance to an antigen which is greater than what would be seen if a method of the invention were not employed. Tolerance, as used herein, refers to a donor antigen-specific inhibition of the immune system as opposed to the broad spectrum inhibition of the immune system seen with immunosuppressants.
Methods of the invention minimize or eliminate the need for hematopoietic space-creating treatment, e.g., irradiation, in many methods of tolerance induction.
In methods of the invention, the creation of thymic space, e.g., by thymic irradiation, the inactivation of recipient peripheral T cells and thymocytes, and the administration of a sufficiently large number of xenogeneic or allogeneic donor stem cells allows the induction of tolerance without subjection the recipient to WBI. The induction of thymic space can reduce the level of donor reactive thymocytes but additional steps (described herein) can be added to further diminish donor thymocyte reactivity.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.